A method of non-destructively evaluating the integrity of structures is described and applied to structures for which a one dimensional analysis is satisfactory. It is shown how vibration measurements made at a single station in the structure can be used, in conjunction with a suitable theoretical model, to indicate both the location and the magnitude of a defect. Receptance analysis is used in this instance, but the principle is equally applicable to other techniques of mathematical analysis. Experimental results are obtained on a variety of components, including straight prismatic bars, a doubly-tapered bar, and an automobile camshaft, excellent agreement between the predicted and actual damage sites being obtained. The axial mode of vibration is generally used, although somes tests are also carried out successfully in torsion.

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During rescue operations of stranded vessels, it is essential to make immediate and reliable decisions to optimize the successful salvage potential and minimize risks of environmental damages and cost impacts. Pursuant to this scenario, the need arises for a numerical tool, which can more accurately forecast the stability conditions experienced by a vessel after running aground and help in the refloating operations of the unit. This study seeks to develop an adequate calculus systematization, which provides analytical capabilities for operational situations in case of stranding, thereby, supporting the decision-making process in these risk situations. Durante operaciones de rescate de embarcaciones varadas, es esencial tomar decisiones inmediatas y confiables para optimizar el potencial de salvamento exitoso y minimizar el riesgo de daños ambientales e impacto de costos. De acuerdo con este escenario, surge la necesidad para una herramienta numérica, que pueda predecir de manera más precisa las condiciones de estabilidad que esté experimentando la embarcación luego de encallar y ayudar en las operaciones de reflotación de la unidad. Este estudio busca desarrollar una adecuada sistematización de cálculo, que brinde capacidades analíticas para situaciones operativas en caso de encallar, así, apoyar el proceso de toma de decisiones durante estas situaciones de riesgo. Abstract Resumen Estabilidad de embarcaciones con varamiento de punto único

When developing vibration models, so as to reduce model complexity, it is typically expected that good prediction accuracy can be achieved by ignoring the complication of friction. In this paper, the significance of friction between the piston and cylinder on engine block dynamics is shown through simulation in both the time and frequency domains. Simulations and experiments indicate that large differences exist between model predictions for the engine block moment if this friction is not accounted for. This is especially true at low crankshaft rotational speeds when dynamic inertia effects are small. Experiments on a motored single cylinder engine at different average rotational speeds confirm the theory and very good tie-up with predictions is obtained. It is expected that these findings will also have implications for the torsional vibration of the engine.

The torsional vibration of a back-to-back gearbox system has been investigated experimentally and analytically. Gearboxes are typically part of a larger system, or drivetrain, which commonly includes electric motors, shafts, couplings, ball mills, turbines and generators. The dynamics of the system has been shown significantly to influence the gearbox response and requires inclusion in gearbox modelling. Assumptions are commonly made, however, to reduce the degrees of freedom of the model, and system dynamics is subsequently neglected. Receptance methods were applied to model a back-to-back gearbox system and were shown to be an effective modelling technique for geared system analysis. A detailed experimental modal analysis was performed using the swept-sine technique with an a.c. servomotor torsional exciter. Torsional excitation allowed for the dynamic response to be measured up to 1600 Hz. A multi-degree-of-freedom, frequency domain torsional model of the gearbox system was developed using receptances. The model included a combination of lumped-mass elements, and continuous shafts with distributed inertia and hysteretic damping. The modelled torsional natural frequencies were matched to the measured frequencies by the adjustment of system model parameters to achieve a high level of agreement. Matching of system natural frequencies resulted in the accurate prediction of the first nine associated torsional deflected shapes up to 1548 Hz. This paper presents the detailed results of a full torsional, modal analysis of a gearbox system, demonstrating receptance system modelling and an effective method for torsional excitation on rotating machines.